Reports where the effective API key comes from (preference, environment, or none).
Allows or refuses the use of an API key found in the environment. Refused by default: an
environment key is only used once the user has confirmed it, and setting this back to false
stops it being used immediately, wherever it would have been used.
Fetches the ids of the Gemini models that currently support content generation from the
/v1beta/modelsendpoint, retrying transient failures and caching a snapshot for offline use. Returns an empty result when no key is configured; falls back to the cached snapshot on failure.